In recent years, organic EL devices have been put to practical use as light emitting display devices in which a plurality of organic EL elements are arranged in a column direction and a row direction in a matrix on a substrate. In such organic EL devices, the organic EL elements are self-luminous, therefore having high visibility, and are entirely solid-state, therefore having excellent impact resistance.
In an organic EL device, each organic EL element typically has a structure in which a light emitting layer that includes an organic light emitting material is disposed between an anode and cathode pair of electrodes. When driven, voltage is applied between the pair of electrodes, holes are injected into the light emitting layer from the anode, electrons are injected into the light emitting layer from the cathode, and the holes and the electrons recombine to emit light. In an organic EL device of a full-color display, such organic EL elements form RGB sub-pixels, a single pixel being formed from a combination of neighboring RGB sub-pixels.
In the organic EL device, a light emitting layer of an organic EL element is typically separated from light emitting layers of neighboring organic EL elements by banks composed of an insulating material. Further, a hole injection layer, a hole transport layer, or a hole injection and transport layer are interposed between the anode and the light emitting layer, as required, and an electron injection layer, an electron transport layer, or an electron injection and transport layer are interposed between the cathode and the light emitting layer, as required. Layers such as a hole injection layer, a hole transport layer, a hole injection and transport layer, an electron injection layer, an electron transport layer, and an electron injection and transport layer are generically referred to as functional layers.
When manufacturing such an organic EL device, there is a process of forming a plurality of banks extending in one direction over a substrate, and forming a functional layer in each of a plurality of groove regions defined by the banks, as indicated in Patent Literature 1. Ink for forming the light emitting layer, including macromolecular material and small molecules with good thin-film formation properties, is often used in a wet process of applying to concave spaces using a method, such as an inkjet method, when forming the functional layer. According to such a wet process, the light emitting layer may be formed with comparative ease despite the panel being large.
As it happens, in certain situations, an amount of the ink applied to each of the groove regions differs among the groove regions defined by the banks because the functional layer is formed for red, green, and blue sub-pixels.
For example, a set film thickness for the hole transport layer and the light emitting layer may differ among red light emitting elements, green light emitting elements, and blue light emitting elements, and the amount of ink applied to the respective groove regions may also differ.